Method for controlling the flow of gases



June 30, 1942. .1. M. NAIMAN METHOD FOR CONTROLLING THE FLOW OF GASES Filed April 2, 1940 INVENTQR Jalzus A1. AZuman TORNEY Patented June 30, 1942 UNITED STATES: Y-PATENT FFICE METHOD non oon'raoumc run now or GASES Julius M. Naiman, Detroit, Mich. Application April 2, 1940, Serial No. 327,412

1 Claim.

This invention relates to a method of distributing gases or vapors to a plurality of parallel zones and more particularly to a method of distributing gases from an inlet header to a bank of tubes.

An object of the invention is to maintain a predetermined gas distribution to a set of tubes regardless of variations in the pressure drops or in the operating conditions within the individual tubes.

Another object is to provide a system of the above type in which changes in operating conditions in one tube of a bank are prevented from afiecting the rate of gas flow to the other tubes of the bank.

Another object is to provide a means for effecting the above control which is automatic in operation and which does not require careful adjustment.

Another object'is to provide a system for ef iecting a desired distribution of gases to a plurality of banks of tubes in a converter furnace.

Another object is to provide an efllcient, de-' tributing gases to a catalytic converter in which the pressure drop within the individual catalyst tubes may vary due to carbon deposition or other change in the condition of the catalyst. and permits the .gas distribution to and through the tubes to be maintained in a predetermined relationship, which is unaffected by conditions within the converter itself, at least until the ical velocity of a gas through a passage such as an orifice, nozzle, Venturi tube or the like. It has been found, for example, that when the absolute pressure on the high'pressure side of such a passage bears a definite relationship to the absolute pressure on the low pressure side thereof, there exists a' condition of maximum velocity and maximum gas flow through the passage for that particular high pressure. This maximum velocity is referred to herein as the critical velocity of the passage. When a passage or the above type is operated under critical pressure conditions, changes in pressure on the low pressure side do not affect the rate of gas flow therethrough, provided the pressure at no time exceeds that required for the critical velocity relationship. Consequently, by incorporating such passages in the individual tubes of a bank and operating the bank of tubes so that the condition of critical velocity exists, variations in pressure within the tubes themselves produced. for example, by changes in pressure drop within the tubes, do not change the rate of gas flow either -in the individual tubes or in the bank of tubes.

pressure drop within an individual tube has increased to a point such that the critical velocity relationship no longer exists.

The critical velocity condition of an orifice nozzle, Venturi tube or other passage depends upon the shape of the particular passage. Critical velocity conditions exist through a sharp edge orifice, for example, when the absolute pressure on the high pressure side is at least double the absolute pressure on the low pressure side. The conditions for other passages may be readily computed or determined.

Although the novel features which are believed to be characteristic of this invention are pointed out more particularly in the claim appended hereto, the invention itself may be better understood by referring to the following description, taken in connection with the accompanying drawing, in which a specific embodiment thereof has been set forth for purposes of illus tration. I

In the drawing,

Fig. 1 is a sectional view through a portion of a converter embodying the present invention;

ically a tube still, a catalytic converter or other device employing a plurality-oi banks of tubes H to which gases are to be distributed.

The tubes H are shown as arranged in four banks. The tubes or each bank communicate with a separate header l4. Gases are supplied to the headers ll from an inlet pipe it through branches I5 and valves II, by means of which the pressure of the gases in the different headers l4 may be controlled.

.Each of the tubes II is shown in Figs. 2 and 3 as provided with a coupling flange 26 which is adapted to beclamped by bolts 2i against a coupling flange 22 on a nipple 24 communicating with the header ll. In the embodiment This invention is particularly useful for disshown an orifice plate 25 is clamped between the.

fianges II and 22. This orifice plate is shown as provided with a gas passage or orifice II of the sharp edge type. It is to be understood,

aaaaaov remaining tubes provided the critical velocity however, that the gas passage may be of otherv conditionsare still maintained. The invention is accordingly suited for the control of gas iiow to a set oi catalyst tubes or banks of tubes, some or which are to be periodically removed from stream for reactivation. It is also useful to maintain constant operating conditions in the various tubes of a bank regardless of changes in fiow through certain tubes due to carbon deposition or the like.

It is to be understood that the above embodiment oi the invention has been given as an illustration only and that the invention may be apabsolute pressure on the low pressure side oi.

the plates N. For example, it the gases are supplied through the pipe I! to the headers ll under a pressure or, say, 80 lbs. absolute, the pressure within the tubes II should not exceed 30 lbs. absolute.

This latter pressure is governed by the back pressure on the system which may be maintained by suitable valves, not shown. The pressure on the low pressure side of the orifice plates will amount to the sum 01 the pressure maintained at some further point in the system and the pressure drop between that point and the orifice plate. This pressure drop is dependent, among other things, upon the condition of the material within the tubes, in the case of a catalytic converter, for example, being dependent upon condition of the catalyst as to porosity. free space, etc.

With the system operating as above set forth and assuming an absolute pressure or 60 lbs. in the headers ll, the pressure in the tubes ii may vary, for example, from 10 lbs. to 28 lbs. without changing the flow through the orifices or the relative distribution of gases to the various tubes.

The gas fiow is accordingly made independent of the condition of the catalyst and the gas distribution is maintained constant without the necessity for accurate or careful adjustments. Even the complete shut down of one or more tubes will not alter the gas flow through the plied with suitable changes in the pressure rela tlonship to passages of various shapes.

While the invention is particularly applicable to the catahrtic treatment of hydrocarbon oils wherein the control of the rate of gas fiow is important, it is to be understood that the invention may be put to other uses and that various changes and modifications may be made therein as will be readily apparent to a person skilled in the art. The invention is only to be limited in accordance with the scope of the following claim.

What is claimed is:

The method of controlling the how of gases through a bank of tubes having flow restricting inlet orifices and connected in parallel between an inlet and an outlet header and in which each of such tubes is subject to varying flow resistances during operation and in a manner such that the flow through each individual tube will be constant regardless of such variations in fiow resistance, which method comprises maintaining a constant high pressure in the inlet header and a sufilciently low pressure in the outlet header that the pressure diiierential across each of said orifices is always suillcient to maintain the diflerential required for critical flow velocity conditions through each of said orifices notwithstanding variations in flow resistance in any or all oi said tubes.

JULIUS M. NAIMAN. 

